It is known practice to dye keratin fibers, for example, human hair, with dye compositions comprising oxidation dye precursors, for instance, ortho- and para-phenylenediamines, ortho- or para-aminophenols, and heterocyclic compounds such as diaminopyrazole derivatives, generally called oxidation bases. Oxidation dye precursors, or oxidation bases, are colorless or weakly colored compounds which, when combined with oxidizing products, can give rise, by means of an oxidative condensation process, to colored and coloring compounds.
It is also known that the shade obtained with these oxidation bases can be varied by combining them with couplers or coloration modifiers, the latter being chosen, for example, from aromatic meta-diamines, meta-aminophenols, meta-diphenols, and certain heterocyclic compounds.
The variety of molecules available as oxidation bases and couplers makes it possible to obtain a rich palette of colors.
“Permanent” dyeing obtained by virtue of these oxidation dyes ideally satisfies at least one of certain characteristics. For example, the dye ideally has no drawbacks in terms of toxicology, makes it possible to obtain shades with the desired intensity, exhibits good resistance to outside agents (for instance, light, bad weather, washing, permanent-waving, perspiration, and/or rubbing), makes it possible to cover white hairs, is as unselective as possible, i.e., makes it possible to obtain the smallest possible differences in coloration along the same keratin fiber, which may be differently sensitized (i.e., damaged) from its tip to its root, and exhibits good chemical stability in the formulations and a good toxicological profile.
Furthermore, for certain applications, it is desirable to have dyes that give chromatic shades on the hair.